/*
 * @TAG(OTHER_GPL)
 */
/* Return backtrace of current program state.
   Copyright (C) 2003-2005,2007,2009,2011,2012 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

//#include <bits/libc-lock.h>
#include <dlfcn.h>
//#include <execinfo.h>
#include <stdio.h>
#include <stdlib.h>
#include "unwind.h"

struct trace_arg {
    void **array;
    _Unwind_Word cfa;
    int cnt;
    int size;
};

#ifdef SHARED
static _Unwind_Reason_Code(*unwind_backtrace)(_Unwind_Trace_Fn, void *);
static _Unwind_Ptr(*unwind_getip)(struct _Unwind_Context *);
static _Unwind_Word(*unwind_getcfa)(struct _Unwind_Context *);
static void *libgcc_handle;


/* Dummy version in case libgcc_s does not contain the real code.  */
static _Unwind_Word dummy_getcfa(struct _Unwind_Context *ctx __attribute__((unused)))
{
    return 0;
}


static void init(void)
{
    libgcc_handle = __libc_dlopen("libgcc_s.so.1");

    if (libgcc_handle == NULL) {
        return;
    }

    unwind_backtrace = __libc_dlsym(libgcc_handle, "_Unwind_Backtrace");
    unwind_getip = __libc_dlsym(libgcc_handle, "_Unwind_GetIP");
    if (unwind_getip == NULL) {
        unwind_backtrace = NULL;
    }
    unwind_getcfa = (__libc_dlsym(libgcc_handle, "_Unwind_GetCFA")
                     ? : dummy_getcfa);
}
#else
# define unwind_backtrace _Unwind_Backtrace
# define unwind_getip _Unwind_GetIP
# define unwind_getcfa _Unwind_GetCFA
#endif

static _Unwind_Reason_Code backtrace_helper(struct _Unwind_Context *ctx, void *a)
{
    struct trace_arg *arg = a;

    /* We are first called with address in the __backtrace function.
       Skip it.  */
    if (arg->cnt != -1) {
        arg->array[arg->cnt] = (void *) unwind_getip(ctx);

        /* Check whether we make any progress.  */
        _Unwind_Word cfa = unwind_getcfa(ctx);

        if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
            && cfa == arg->cfa) {
            return _URC_END_OF_STACK;
        }
        arg->cfa = cfa;
    }
    if (++arg->cnt == arg->size) {
        return _URC_END_OF_STACK;
    }
    return _URC_NO_REASON;
}

int
backtrace(array, size)
void **array;
int size;
{
    struct trace_arg arg = { .array = array, .cfa = 0, .size = size, .cnt = -1 };
#ifdef SHARED
    __libc_once_define(static, once);

    __libc_once(once, init);
    if (unwind_backtrace == NULL) {
        return 0;
    }
#endif

    if (size >= 1) {
        unwind_backtrace(backtrace_helper, &arg);
    }

    /* _Unwind_Backtrace seems to put NULL address above
       _start.  Fix it up here.  */
    if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL) {
        --arg.cnt;
    }
    return arg.cnt != -1 ? arg.cnt : 0;
}
//weak_alias (__backtrace, backtrace)
//libc_hidden_def (__backtrace)


#ifdef SHARED
/* Free all resources if necessary.  */
libc_freeres_fn(free_mem)
{
    unwind_backtrace = NULL;
    if (libgcc_handle != NULL) {
        __libc_dlclose(libgcc_handle);
        libgcc_handle = NULL;
    }
}
#endif
